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Tuberculosis (TB): Latent TB Infection

The World Health Organization (WHO) estimates that 1 in 3 living today has latent TB infection. From this reservoir of 2 billion come roughly 9 million new cases annually. Cases range widely by continent/nation. Africa, Asia, the Indian subcontinent and Latin America typically range from 200 to 400 cases per 100,000 population annually. By contrast, cases in the U.S. and Canada are now about 10 per 100,000.

In the U.S. over 60% of new cases are seen in the foreign born. Case rates in the U.S. are highest among Asians, ranging down among Hispanics, African Americans, Native Americans and Caucasians.

Most cases among Caucasians are among the elderly who were infected decades ago. By contrast, there are higher rates among infants and early adulthood among minorities.

Treatment for Latent TB Infection

Treatment for latent TB infection is usually a single antibiotic for nine months. The goal of this treatment is to eliminate the bacteria from your body. A long treatment is required because antibiotics work only when the bacteria are actively dividing, and the bacteria that cause TB can rest without growing for long periods. This treatment is necessary to keep the latent TB infection from developing into active disease.

Isoniazid (INH) is the most commonly prescribed antibiotic for latent TB. INH can cause liver damage with long-term use, so your doctor may monitor your liver with blood tests over the months that you take the drug. You should avoid acetaminophen (Tylenol) and alcohol while taking INH, as these can also cause liver damage. (Symptoms of liver damage include nausea, vomiting, yellow discoloration of the eyes, fever, and diarrhea.) Some people who do not have a positive skin test take INH because their history of exposure to someone with active disease makes it likely that they have been infected.

Some drugs taken for other conditions increase the risk that a latent TB infection will become active; be sure to tell your doctor about all drugs that you are taking.